Method and system for computing and sending resource requests and avoiding deadlock situations in mobile communication system

ABSTRACT

Disclosed is a method for transmitting a buffer status report (BSR) by a terminal performing a handover procedure from a first network element to a second network element in a mobile communication system, including identifying a data packet available for transmitting and packet data convergence protocol (PDCP) control information, generating a BSR based on the data packet and the PDCP control information, the PDCP control information including header compression control information and a PDCP status report indicating which PDCP data is missing, and transmitting the generated BSR to the second network element, wherein the PDCP status report is transmitted to the second network element based on the BSR as a first PDCP PDU during the handover procedure performed by the terminal.

PRIORITY

This application is a Continuation Application of U.S. patentapplication Ser. No. 12/696,784, which was filed in the U.S. Patent andTrademark Office on Jan. 29, 2010, and claims priority to IndianProvisional Application No. 212/CHE/2009 filed in the Indian PatentOffice on Jan. 29, 2009 and Indian Complete Application No. 212/CHE/2009filed in the Indian Patent Office on Jan. 19, 2010, the contents of eachof which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a wireless communicationsystem, and more particularly, to a resource request procedure in awireless communication system.

2. Description of the Related Art

Several generations of communication networks, such as radiocommunication systems, have been developed to this point. Such radiocommunication systems include the First Generation system (1G), SecondGeneration system (2G), Third Generation system (3G) and FourthGeneration system (4G). Each generation has different transmissioncharacteristics and communication technologies.

The 1G systems, such as Advanced Mobile Phone System (AMPS), and TotalAccess Communications System (TACS), is based on analog frequencymodulation technology. The 2G system, such as Global System for Mobilecommunications (GSM), is based on Time Division Multiple Access (TDMA).The 3G systems, such as Universal Mobile Telecommunications System(UMTS) and GSM Evolution (EDGE), are based on a Wideband Code DivisionMultiple Access (WCDMA) air interface. The 4G system is an InternationalTelecommunication Union (ITU) specification that is presently beingdeveloped for broadband mobile capabilities. The 4G system would enableInternet Protocol (IP) packet-based voice data and streaming multimediaat higher speeds than with the 3G system. Transmission resources in the4G wireless communication systems are shared among many users, such asmobile phones or User Equipments (UEs). Therefore, the data availabilityfor transmission is reported by the UE to network element, such as anevolved (e) NodeB, to receive transmission resources (correspondinggrants) from the network for the actual transmission of the data. Thereport is called a Buffer Status Report (BSR).

However, for calculating BSR, the data that arrives from higher layersin a protocol stack are accounted for transmission. As such, noconsideration is given in the BSR for packets generated at other layers.Further, a Packet Data Convergence Protocol (PDCP) status report that iscapable of preventing the occurrence of data loss is also not consideredfor BSR. The PDCP status report conveys to the peer entity the receptionstatus of the PDCP Protocol Data Units (PDU) following a handover.

The application or upper layer data packet termed as Service Data Units(SDU) is processed at the PDCP layer, and the resultant data packetformed is termed a PDU. The PDCP status report carries informationindicating whether reception of the PDUs is successful. For example, thePDCP report includes information about the PDU(s) that have beenreceived successfully and the PDU(s) that were not received or weremissing, thus needing retransmission. Hence, the size of the PDCP statusreport is variable.

Thus, during handover, a peer entity (network) performs transmissionsand retransmissions on the basis of the PDCP status report to achieve alossless handover. Therefore, the PDCP status report should also beconsidered for BSR. Currently, the PDCP report is not considered forcomputing data availability for transmission, and as such, the reportedBSR conveyed to the network is not accurate enough.

A network element computes on the basis of the received BSR and providesgrants to the UE. The grants provided would not match the actualtransmission requirements at the UE. There may be a case in which somedata may incur a delay in transmission until sufficient grants aresubsequently received. When there is no application or upper layer dataexisting, the existing method would send a BSR conveying zero value.However, there may be PDCP status report available which needs to betransmitted.

Therefore, when no user data is available, the BSR report makes norequirements and thus, no grant is fetched. Hence, a PDCP status reportcannot be transmitted. The PDCP Status Report is mandated as the firstUpLink (UL) packet (in some access technologies) after the handover;therefore, absence of a grant to send the status report will result in adeadlock situation.

This deadlock cannot be broken until some new user data or applicationdata arrives. However, any delay in transmission of a PDCP status reportin UL would cause the DownLink (DL) to also suffer, and the networkwould not perform timely transmissions and retransmissions. When thenetwork element discovers a zero requirement BSR, it may discard thepackets which otherwise would need to be re-transmitted to the UE basedon its PDCP Status Report, thus incurring packet losses on the bearer.

Also, to achieve a desired Quality of Service (QoS), the network elementlimits the maximum delay in transmitting the upper layer. Thus,application data is subject to an expiration of the discard timer, andthe corresponding user data is discarded. During handover scenarios, itis likely that the upper layer data, which was available beforehandover, gets discarded after handover completion based on the discardtimer(s) expiration. The timing values for discard timers and handoverprocedure completion are comparable.

Although the header compression feedback related control information isgenerated at the PDCP layer, there would be a mismatch in actualtransmission resource requirement and the reported BSR (and thereby theallocated grant), as the header compression feedback related controlinformation is not accounted for BSR, resulting in transmission delay ofsome data. Another adverse effect is that the data packets would undergoan undesired segmentation/re-segmentation for requesting of a sufficientgrant, thereby leading to increased processing complexity andinefficiency at the UE.

Hence, there exists a need for a method to efficiently manage resourcerequirements in the mobile communication network.

SUMMARY OF THE INVENTION

An embodiment of the present invention discloses a method fortransmitting a buffer status report (BSR) by a terminal performing ahandover procedure from a first network element to a second networkelement in a mobile communication system, including identifying a datapacket available for transmitting and packet data convergence protocol(PDCP) control information, generating a BSR based on the data packetand the PDCP control information, the PDCP control information includingheader compression control information and a PDCP status reportindicating which PDCP data is missing, and transmitting the generatedBSR to the second network element, wherein the PDCP status report istransmitted to the second network element based on the BSR as a firstPDCP PDU during the handover procedure performed by the terminal.

Another embodiment of the present invention, a terminal for transmittinga buffer status report (BSR) while performing a handover procedure froma first network element to a second network element in a mobilecommunication system includes a processor for identifying a data packetavailable for transmitting and packet data convergence protocol (PDCP)control information, generating a BSR based on the data packet and thePDCP control information, the PDCP control information including headercompression control information and a PDCP status report indicatingwhich PDCP data is missing, and transmitting the generated BSR to thesecond network element, and a transceiver for transmitting the generatedBSR to a first network element, wherein the PDCP status report istransmitted to the second network element based on the BSR as a firstPDCP PDU during the handover procedure performed by the terminal.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates an environment, in which various embodiments of thepresent invention may be practiced;

FIG. 2 illustrates a first network element, in accordance with anembodiment of the present invention;

FIG. 3 illustrates a method for requesting resources to send datapackets in a mobile communication system, in accordance with a firstembodiment of the present invention; and

FIG. 4 illustrates a method for requesting resources to send datapackets in a mobile communication system, in accordance with a secondembodiment of the present invention.

Persons skilled in the art will appreciate that elements in the figureis illustrated for simplicity and clarity and may have not been drawn toscale. For example, the dimensions of some of the elements in the figuremay be exaggerated relative to other elements to help to improveunderstanding of various embodiments of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The following definitions of certain words and phrases used throughoutthis patent document are set forth. The terms “include” and “comprise,”as well as derivatives thereof, mean inclusion without limitation; theterm “or,” is inclusive, meaning and/or; the phrases “associated with”and “associated therewith,” as well as derivatives thereof, may mean toinclude, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, or the like. Definitions for certainwords and phrases are provided throughout this patent document, andthose of ordinary skill in the art should understand that in many, ifnot most instances, such definitions apply to prior, as well as futureuses of such defined words and phrases.

Those skilled in the art will understand that the principles of thepresent disclosure may be implemented in any suitably arrangedcommunications system. The terms used to describe various embodimentsare provided to merely aid the understanding of the description, andtheir use and definitions in no way limit the scope of the invention.Terms first, second, and the like are used to differentiate betweenobjects having the same terminology and are not intended to represent achronological order, as and where stated otherwise. Detaileddescriptions of well-known functions and structures incorporated hereinmay be omitted for the sake of clarity and conciseness.

FIG. 1 illustrates an environment 100 in which various embodiments ofthe present invention may be practiced. The environment 100 includes aUE 102 and a first network element 104 in a 4G mobile communicationnetwork 100. Although a 4G network is described, the present inventionis not limited thereto. The environment 100 can also include a greateror lesser number of system elements to perform the method.

In the environment 100, at step 106 an amount of data packets availablefor transmission is reported by the UE 102 to the first network element104 in a request for resource allocation. Examples of the networkelement include, but are not limited to, eNodeB, Base TransceiverStation (BTS) and Radio Network Controller (RNC). Therefore, the amountof data packets available for transmission is reported by the UE 102(mobile phone), through a BSR, to the first network element 104 (eNodeB)to receive corresponding grants (transmission resources) from the firstnetwork element 104 for an actual transmission of the data packets.

The BSR is calculated based on the data packets that are received fortransmission from higher layers, the data packets generated at otherlayers, and ROHC feedback. In an embodiment, a PDCP status report thatis capable of preventing occurrence of data loss is also considered forthe BSR. The PDCP status report conveys to a peer entity a receptionstatus of the PDCP data, such as PDUs, following the handover.

In an embodiment, the amount of data packets is calculated based on theamount of Service Data Units (SDUs), the amount of PDUs and the size ofan ROHC feedback. The SDUs are the data packets sent by a user of theservices of a given layer and are available for transmission. The SDUsare processed at a PDCP layer to form packet data and are termed asPDUs. For calculating the BSR, both PDUs and SDUs are considered. Thedata packets available for transmission at the PDCP layer are computedand are considered in the BSR. In an embodiment, the SDUs at the PDCPlayer are considered in the BSR, if PDUs for the corresponding SDU havenot been submitted to lower layers and/or if the SDUs have not beenprocessed by PDCP. The PDU are considered if the SDU has been processedat the PDCP layer.

The control information generated at the layer, for example headercompression control information, is considered as data available fortransmission in the PDCP layer. When a handover occurs, the PDCP layerreceives an indication from upper layer that a handover has occurred,and the SDUs are identified for which a corresponding PDU has beensubmitted to lower layers prior to handover and the successful deliveryassociated with the SDU that has not been confirmed by lower layers orby a PDCP status report. The SDUs are then considered if the SDU has notbeen processed at the PDCP layer. The PDU are considered in the BSR ifthe SDUs have been processed by PDCP. Thus if the PDCP status report isavailable, the PDCP status report is also considered as data availablefor transmission in the PDCP layer.

Thereafter, the first network element 104 computes on the basis of thereceived BSR report and provides grants to the UE 102 at step 108. Thusthe PDCP Status report and ROHC feedback are also considered in the BSRas data available for transmission. The method provides an enhanced andaccurate reporting of the data availability for the transmission.Consequently, an improved match is created between the actualtransmission resource requirement and the reported BSR (and thereby theallocated grants). Thus a possibility of deadlock in handover scenariosis avoided by including PDCP status report in the reported BSR.

FIG. 2 illustrates a UE, in accordance with an embodiment of the presentinvention. Although references will be made to FIG. 1, it will beapparent to a person ordinarily skilled in the art that the embodimentof FIG. 2 can be explained with the help of any other suitableembodiment of the present invention. The UE 102 includes a processor 202and a transceiver 204.

The processor 202 in the UE 102 identifies an amount of data packetsavailable for transmitting to a first network element. The data packetsinclude SDUs and PDUs. The processor 202 then calculates size of an ROHCfeedback packet associated with the data packets available fortransmitting to the first network element 104. The ROHC is astandardized method to compress the Internet Protocol (IP), UserDatagram Protocol (UDP), and Transmission Control Protocol (TCP) headersof Internet packets.

The processor 202 creates a BSR based on the amount of data packetsavailable for transmitting and the size of the ROHC feedback packet. Thetransceiver 204 thereafter sends the BSR created by the processor 202 tothe first network element 104 to allocate resource(s) for the UE 102 forsending the data packets available for transmitting along with ROHCfeedback packet.

The processor 202 performs handover procedures when the UE 102 movesfrom the first network element 104 to the second network element.Thereafter, the processor 202 identifies a size of a PDCP status reportbased on the handover procedure, and prepares a buffer status reportbased on the PDCP status report and available data packets. Thereafter,the transceiver 204 sends the buffer status report to the second networkelement when the UE 102 performs the handover procedure from a firstnetwork element 104 to the second network element.

FIG. 3 illustrates a method at a UE for requesting resources to senddata packets in a mobile communication system, in accordance with afirst embodiment of the present invention.

Examples of mobile communication systems in FIG. 3 include, but are notlimited to, Long Term Evolution (LTE) system, Universal MobileTelecommunications System (UMTS), 3rd Generation Partnership Project(3GPP) and Worldwide Interoperability for Microwave Access (WiMax)systems. In the environment 100, the mobile communication system is a4^(th) Generation mobile communication system. Hence, in an environment100, the UE 102 is a mobile device and the first network element 104 iseNodeB.

At step 302, the method 300 is initiated. At step 304, the UE 102identifies an amount of data packets available for transmitting to afirst network element, such as the first network element 104. Examplesof the first network element are NodeB, eNodeB, Base Transceiver Station(BTS), and Radio Network Controller (RNC). The data packets include SDUsand/or PDUs. The SDU is a data packet that arrives at a certain layerfor processing by a said layer. The processed data packet is a PDU andis passed on to the layer underneath the said layer. In an embodiment,the header of the data packets available for transmitting to the firstnetwork element 104 is compressed before sending. The compression of thedata packets available is performed at a PDCP layer.

At step 306, the method calculates size of an ROHC feedback packetassociated with the data packets available for transmitting to the firstnetwork element 104. The ROHC technique is used to compress headers ofthe data packets (SDU and PDU) available for transmitting to the firstnetwork element 104. At step 308, the method 300 creates a BSR based onthe amount of data packets available for transmitting and the size ofthe ROHC feedback packet.

At step 310, the BSR is sent to the first network element 104 toallocate resource(s) to the UE 102 for sending the data packetsavailable for transmitting along with ROHC feedback packet. The BSR issent to the second network element when the UE performs a handover fromthe first network element 104 to a second network element. The method ofFIG. 3 identifies a size of the PDCP status report based on the handoverprocedure. The BSR is estimated based on the size of the PDCP statusreport, the amount of data packets available for transmitting and thesize of the ROHC feedback packet. At step 312 the method is terminated.

FIG. 4 illustrates a flow chart depicting a method at a UE forrequesting resources to send data packets in a mobile communicationsystem, in accordance with a second embodiment of the present invention.

At step 402 the method is initiated. At step 404, a handover procedureis performed from the first network element 104 to a second networkelement, both of which being an eNodeB. During the handover, the datapackets information is transferred from the first network element to thesecond network element. The data packets are at least one of SDUs andPDUs.

At step 406, a size of the PDCP status report is identified based on thehandover procedure. The PDCP status report includes informationindicating whether reception of PDU(s) at the second network element issuccessful. For example, the PDCP report includes information about thePDU(s) that have been received successfully, and the PDU(s) that werenot received or were missing, thus requiring a retransmission. Hence,the size of the PDCP status report is variable.

At step 408, a buffer status report is prepared based on a PDCP statusreport and available data packets. The inclusion of PDCP status reportsize in the BSR provides the UE 102 with a resource grant which is usedto transmit PDCP status report even in absence of user data, therebyavoiding a deadlock situation when no resource and transmission occurs.

At step 410, the BSR is sent to the second network element when the UE102 performs handover from the first network element 104 to the secondnetwork element. The PDCP status report is sent via UL as a first packetto the second network element, after or during a handover procedure. Atstep 412 the method is terminated.

As described above, the foregoing embodiments of the present inventionprovide an efficient method for requesting resources to send datapackets in a mobile communication system. A method calculates anappropriate BSR for requesting resources. Hence, the method increasesaccuracy of the reported BSR. A method provides an enhanced and accuratemethod of reporting data availability for transmission, and enhances BSRaccuracy by introducing the PDCP Status report and ROHC feedback.

A method mandates transmission of the PDCP status report as the first ULpacket following a handover and thereafter the upper layer orapplication data packets are transmitted. Hence, in the absence of upperlayer data during handover scenario reports, the BSR accounts for onlyan available status report and avoids any deadlock possibility inhandover scenarios. The method achieves speedy and lossless handover inthe mobile communication system, and avoids a delay in transmission andretransmissions.

The present invention and its advantages have been described withreference to specific embodiments. However, it will be apparent to aperson of ordinary skill in the art that various modifications andchanges can be made, without departing from the scope of the presentdisclosure, as set forth in the claims below. Accordingly, thespecification and figures are to be regarded as illustrative examples ofthe present disclosure, rather than in restrictive sense. All suchpossible modifications are intended to be included within the scope ofpresent disclosure.

Embodiments of the present disclosure are related to the use of thecomputer system for implementing the techniques described herein. In anembodiment, the techniques are performed by the processor by usinginformation included in the memory. Such information can be read intothe main memory from another machine-readable medium, such as storagedevice. The information included in the memory causes the processor toperform the method described herein.

The term “machine-readable medium” as used herein refers to any mediumthat participates in providing data that causes a machine to operationin a specific fashion. In one embodiment which is implemented using thecomputer system, various machine-readable mediums are involved, forexample, in providing information to the processor for execution. Themachine-readable medium can be a storage media. Storage media includesboth non-volatile media and volatile media. Non-volatile media includes,for example, optical or magnetic disks, such as server storage unit.Volatile media includes dynamic memory. All such media must be tangibleto enable the information carried by the media to be detected by aphysical mechanism that reads the information into a machine.

Common forms of machine-readable medium include, for example, a floppydisk, a flexible disk, hard disk, magnetic tape, or any other magneticmedium, a CD-ROM, any other optical medium, punch cards, paper tape, anyother physical medium with patterns of holes, a RAM, a PROM, and EPROM,a FLASH-EPROM, any other memory chip or cartridge.

In another embodiment, the machine-readable medium can be a transmissionmedia including coaxial cables, copper wire and fiber optics, includingthe wires that include bus. Transmission media can also take the form ofacoustic or light waves, such as those generated during radio-wave andinfra-red data communications. Examples of machine-readable medium mayinclude, but are not limited to, a carrier wave as or any other mediumfrom which a computer can read, for example online software, downloadlinks, installation links, and online links.

What is claimed is:
 1. A method for transmitting a buffer status report(BSR) by a terminal performing a handover procedure from a first networkelement to a second network element in a mobile communication system,the method comprising: identifying a data packet available fortransmitting and packet data convergence protocol (PDCP) controlinformation; generating a BSR based on the data packet and the PDCPcontrol information, the PDCP control information including headercompression control information and a PDCP status report indicatingwhich PDCP data is missing; and transmitting the generated BSR to thesecond network element, wherein the PDCP status report is transmitted tothe second network element based on the BSR as a first PDCP PDU duringthe handover procedure performed by the terminal.
 2. The method of claim1, wherein the data packet is at least one of service data units (SDUs)and PDUs.
 3. The method of claim 1, wherein the first network element isan evolved node B (eNodeB).
 4. The method of claim 1, wherein the mobilecommunication system is a long term evolution (LTE) system.
 5. Aterminal for transmitting a buffer status report (BSR) while performinga handover procedure from a first network element to a second networkelement in a mobile communication system, the terminal comprising: aprocessor for identifying a data packet available for transmitting andpacket data convergence protocol (PDCP) control information, generatinga BSR based on the data packet and the PDCP control information, thePDCP control information including header compression controlinformation and a PDCP status report indicating which PDCP data ismissing, and transmitting the generated BSR to the second networkelement; and a transceiver for transmitting the generated BSR to a firstnetwork element, wherein the PDCP status report is transmitted to thesecond network element based on the BSR as a first PDCP PDU during thehandover procedure performed by the terminal.
 6. The terminal of claim5, wherein the data packet is at least one of service data units (SDUs)and PDUs.
 7. The terminal of claim 5, wherein the first network elementis an evolved node B (eNodeB).
 8. The terminal of claim 5, wherein themobile communication system is a long term evolution (LTE) system.